A precision vacuum seeder was modified to allow simultaneous
mounting of two different furrow openers,with one furrow opener
on one row unit and the second furrow opener on another row unit,
on the two-row seeder. The seeder was a general-purpose
Sonmezler PMD seeder designed for row crops such as maize
and soybean (Fig. 1) (Sonmezler Company, Adana, Turkey). A seed
plate operated in a vertical plane and required a vacuum of 3.5–
8.0 kPa to select a seed. Air suction from the holes of the seed plate
caused the seed to stick to holes 4 mm in diameter